1. Field of the Invention
The present invention relates to a liquid storage container, a liquid ejecting device and a liquid ejecting apparatus with improved liquid supply property.
The present invention can be applied to a facsimile equipped with a copying unit and a communication unit, a word processor equipped with a printing unit etc. and moreover a printing apparatus for an industrial use combined with various processing units as well as an ordinary printing apparatus.
2. Brief Description of the Related Arts
Generally speaking an ink tank (a tank built in a recording head and an exchangeable tank is included) equipped into a printing apparatus in an ink-jet recording method, has a constitution capable of adjusting holding property of ink (Here a liquid used for enhancing a recording quality and so on is included in ink.) stored in the ink tank so as to supply the ink in a good condition to a recording head to eject ink. Since the holding property renders a pressure at ejection ports of the recording head negative against the atmosphere, it is called a negative pressure. (Hereinafter a member that generates such negative pressure is also referred as a xe2x80x9cnegative pressure generating memberxe2x80x9d.)
As one of the easiest ways to generate the negative pressure, a method to utilize a capillary effect of the negative pressure generating member formed out of polyurethane foam equipped in the ink tank is often employed.
The applicant proposed in a laid-open Japanese patent No. 8-20115 an ink tank which employs fibers out of a polyolefine thermoplastic resin having various excellent properties against ink as the negative pressure generating member (A negative pressure generating member employed such fibers is also referred as xe2x80x9ca fiber absorberxe2x80x9d.)
This ink tank bears not only excellent storage stability but also an excellent recycling property, since the tank body and the negative pressure generating member are formed out of the same kind of material.
The applicant also proposed in laid-open Japanese patents No. 7-125232 and No. 6-40043 etc., an ink tank comprised of a compartment accommodating the negative pressure generating member and a compartment accommodating ink together so as to improve volume efficiency of ink in the ink tank (Hereinafter the tank comprised in this way is referred as xe2x80x9can ink tank with double compartmentsxe2x80x9d.).
FIG. 15 shows a sectional schematic constitutional view of the above-mentioned ink tank with double compartments. The inner part of an ink tank 1 constituted in the above-mentioned way is divided by a separating wall 2 having a connecting opening 10 into two compartments one of which is virtually closed except the connecting opening 10 of the separating wall 2 and is used as a liquid accommodating compartment 3 for holding ink directly, and the other compartment is used as a negative pressure generating member accommodating compartment 4 for accommodating a negative pressure generating member 5. On walls comprising the negative pressure generating member accommodating compartment 4, an opening 6 is formed on a top wall 4a for importing air and an opening 8 for ink supply bearing a ink exporting member 7 is formed on a bottom wall 4b for supplying ink to a unshown recording head. In FIG. 15 a portion of the negative pressure generating member 5 which holds ink is shown as an area below a wave formed line. And accommodated ink in the liquid accommodating compartment is depicted with broken lines.
In the above-mentioned structure when ink is consumed at the unshown recording head, the air is imported into the negative pressure generating member accommodating compartment 4 via the opening 6 and enters into the liquid accommodating compartment 3 via the connecting opening 10 on the separating wall 2. In return, ink flows from the ink accommodating compartment 3 via the connecting opening 10 into the negative pressure generating accommodating compartment 4 and filled in the negative pressure generating member 5. (Hereinafter this movement is referred as xe2x80x9ca gas/liquid exchange movement.xe2x80x9d) Consequently, even if ink is consumed at the recording head it is filled in the negative pressure generating member 5 in response to a consumed amount of ink so as to hold a constant amount of ink in the negative pressure generating member 5 and so as to keep the negative pressure against the recording head constant, thus a stable ink supply is attained.
As shown in FIG. 15 spaces where the negative pressure generating member is not filled, are formed by ribs 9 around the opening 6 connected with the atmosphere, namely buffer compartments 11 and an air importing portion 12 to enhance importing air, is formed around the connecting opening 10 between the negative pressure generating member compartment 4 and the liquid accommodating compartment 3.
In the above-mentioned ink tank with double compartments, contacting portions of the negative pressure generating member 5 with the separating wall 2, particularly a portion of the negative pressure generating member 5 contacting with the air importing portion 12 have a important role for determining an ink supplying property.
Namely, when a contact between the negative pressure generating member 5 and the separating wall 2 is so intimate that the negative pressure generating member 5 in the vicinity of the air importing portion 12 becomes denser, namely, the capillary effect of the portion is raised higher than surrounding portions. As a result, even ink held in the negative pressure generating member 5 is consumed, ink held around the air importing portion 12 is not consumed so that finally the air is not imported into the liquid accommodating compartment 3 and in some cases the ink supplying movement is finished as the ink remains in the liquid accommodating compartment 3.
Usually the negative pressure generating member 5 employed in the ink tank with double compartment has to be inserted into the negative pressure generating member accommodating compartment 4 after compressing the member. Namely, the forced insertion after the compression is necessary to avoid forming unnecessary air gaps that may cause ink drips, when gaps are formed between inner walls of the ink tank and the negative pressure generating member 5 and when the gaps are directly connected with the air. Since there is a probability that a displacement of the negative pressure generating member 5 may occur due to an unexpected fall of the ink tank, it is necessary to fix the negative pressure generating member 5 by the aide of elastic force derived from insertion of the compressed negative pressure generating member 5 with a larger size by a certain margin. However, in this case, as mentioned above, since a density of the portion of the negative pressure generating member 5 around the separating wall 2 becomes higher, in some cases the ink supply may be interrupted.
As measures against the above-mentioned ink interruption, a structure where a density in the portion of the negative pressure generating member 5 corresponding to the air importing portion 12 is reduced by forming the air importing portion 12 inner than the face of the separating wall 2, namely, by forming a negative pressure relaxing portion 13 is proposed. By introducing such structure having the negative pressure relaxing portion a stable gas/liquid exchange is attained due to the enhanced air import.
When the polyurethane foam is employed as the negative pressure generating member 5, a negative pressure relaxing effect is attained by forming the above-mentioned relaxing structure since the polyurethane foam can be pushed into such relaxing structure.
However, the applicant and others have found that in some cases the negative pressure relaxing structure does not function well when a fibrous absorber is employed as the negative pressure generating member in the above-mentioned ink tank with double compartments. Namely, as shown in FIGS. 16A and 16B a portion of the fibrous absorber i.e. the negative pressure generating member contacting with a portion of the separating wall 2 around the air importing portion 12, is collapsed so that enough relaxing effect is not attained due to the raised capillary effect in this portion, and thus the ink supplying procedure is finished before the gas/liquid exchange starts. Even if the gas/liquid exchange is initiated in this status, there may be a probability that the ink supply becomes incapable or the ink ejecting property in the inkjet recording head is badly affected, due to an increased pressure drop between the connecting opening 10 and the opening 8 for ink supply caused by a lowered ink/air interface which is further lowered during the ink supplying procedure.
Through studying the above-mentioned phenomena, the applicant have found the following facts.
{circle around (1)} Since the fibrous absorber is not so elastic as the polyurethane foam due to its materiel property, it is more difficult to receive compression as a whole (particularly the orientation of the absorber affects the compression, in some cases it is more difficult to deform the absorber in an oriented direction) and local collapse (buckling) is apt to occur when a compressed rate (a dimension in a crossing direction to the separating wall of the fiber type absorber before insertion/a corresponding inner dimension of the tank case) of the fibrous absorber exceeds a certain value. {circumflex over (2)} When the crossing direction to the separating wall of the compartment for accommodating the negative pressure generating member is selected as a direction for analysis, the negative pressure generating member receives the same repulsive forces P and p from both sides (from the separating wall 2 and from the opposite wall to the separating wall 2) respectively. However, since xe2x80x9cthe opposite wall to the separating wall 2 and a contacting surface area 18 (a hatched area in FIG. 17A) of the negative pressure generating member 5 with the opposite wallxe2x80x9d is larger than xe2x80x9cthe separating wall around the air importing portion 12 and a contacting area (a hatched area in FIG. 17B) of the negative pressure generating member 5 with the air importing portionxe2x80x9d, a larger pressure is exerted on the side of the separating wall 2 of the negative pressure generating member 5 in terms of a repulsive force per unit area (see FIG. 17C: where a relation P less than p is depicted as lengths of respective arrows.).
As a result, whenever a locally collapsed area 5b is generated, the locally collapsed area 5b is always is generated in the vicinity of the air importing area 12, which causes the above-mentioned poor ink supply (Although, a negative pressure relaxing structure 13 is formed, enough relaxing effects are not attained due to a high capillary effect caused by the collapsed area 5b around an area 5a etc. of the negative pressure generating member 5 in the vicinity of the separating wall 2.)
When the above-mentioned compressed rate is kept in a certain range (Namely, when a dimension dispersion of the negative pressure generating member 5 as the absorber is kept at a lower level.), enough amount of ink supply can be attained by the function of the negative pressure relaxing structure, due to that the collapsed area 5b in the negative pressure generating member 5 is kept small in its size. (In the ink tank with double compartments where presently the fibrous absorber etc. is employed, this is not a too significant problem.)
However, sometimes depend on a fiber type and so on employed in the fibrous absorber for the negative pressure generating member, cut fibers are not precise enough in their sizes In this case, a ink supply is deteriorated by the above-mentioned collapse due to a larger sized fibrous absorber caused by a large dispersion in fiber size of the absorber, which leads to a low production yield.
When an ink-jet printer with higher printing rate and also with more increased ink supply is required, the collapsed areas should be suppressed so as to provide a liquid storage tank with more improved quality.
The objective of the present invention is to provide a liquid storage tank which can realize more stable ink supply, a liquid ejecting device equipped with the liquid storage tank and a liquid ejecting apparatus equipped with the liquid ejecting device by suppressing collapsed areas of the fibrous absorber around the air importing portion in the ink tank with double compartments where the negative pressure generating member such as the fibrous absorber etc. are employed.
In order to attain the above-mentioned objective, a liquid storage tank is consisted of; a negative pressure generating member accommodating compartment accommodating a negative pressure generating member consisting of a fiber material, having a liquid supplying portion and a connecting portion with the atmosphere; a liquid accommodating compartment for storing liquid to be supplied to the negative pressure generating member, having a connecting portion with the negative pressure generating member accommodating compartment and forming an almost closed space; a separating wall separating the negative pressure generating member accommodating compartment from the liquid accommodating compartment and having the connecting portion connecting both compartments; and an air importing portion forming a path for importing air from the negative pressure generating member accommodating compartment to the liquid accommodating compartment in the vicinity of the connecting portion; wherein the liquid storage tank has a means to suppress unnecessary collapsed areas in the negative pressure generating member in the vicinity of the air importing portion.
The liquid storage tank according to the present invention is also characterized by that the tank has a constitution to relax a contact status against a wall facing opposite to the separating wall in the vicinity of the air importing portion as the means to suppress the collapse.
The liquid storage tank according to the present invention is further characterized by that concave portions are formed on the wall facing opposite to the separating wall as the means to relax the above-mentioned contact status. The liquid storage tank according to the present invention is characterized by that a portion of the above-mentioned negative pressure generating member is deformed in a direction so as to be apart from the inner wall as the means to relax the above-mentioned contact status.
The liquid storage tank according to the present invention is also characterized by that the contact area of the concave portions with the negative pressure generating member is smaller than the contacting area in the vicinity of the air importing portion with the negative pressure generating member.
The liquid storage tank according to the present invention is characterized by that the concave portions are comprised by a plurality of grooves in a vertical direction with an opening for air discharge on its upper part.
The liquid storage tank according to the present invention is also characterized by that the concave portions are comprised by a plurality of grooves in a horizontal direction and the neighboring grooves are connected each other via notches.
The liquid storage tank according to the present invention is further characterized by that the negative pressure generating member formed out of the fiber material is comprised by laminated fiber members oriented almost in the same direction so as to cross the separating wall.
And further the liquid storage tank according to the present invention is characterized by that the fiber members are polyolefine resin fibers.
A liquid ejecting device consisted of a liquid storage tank having; a negative pressure generating member accommodating compartment for accommodating a negative pressure generating member consisting of a fiber material, having a liquid supplying portion and a connecting portion with the atmosphere; a liquid accommodating compartment for storing liquid to be supplied to the negative pressure generating member, having a connecting portion with the negative pressure generating member accommodating compartment and forming an almost closed space; a separating wall separating the negative pressure generating member accommodating A compartment from the liquid accommodating compartment and forming the connecting portion connecting both compartments and an air importing portion for importing air from the negative pressure generating member accommodating compartment to the liquid accommodating compartment formed in the vicinity of the connecting portion; and of a recording means by ejected liquid supplied from the liquid storage tank: wherein the liquid storage tank has a means to suppress unnecessary collapsed areas in the negative pressure generating member in the vicinity of the air importing portion.
A liquid ejecting apparatus consisted of a liquid ejecting device having; a negative pressure generating member accommodating compartment for accommodating a negative pressure generating member consisting of a fiber material, having a liquid supplying portion and a connecting portion with the atmosphere; a liquid accommodating compartment for storing liquid to be supplied to the negative pressure generating member, having a connecting portion with the negative pressure generating member accommodating compartment and forming an almost closed space; a separating wall separating the negative pressure generating member accommodating compartment from the liquid accommodating compartment having the connecting portion; an air importing portion for importing air from the negative pressure generating member accommodating compartment to the liquid accommodating compartment formed in the vicinity of the connecting portion; and a recording means by means of ejected liquid supplied from the liquid storage tank; and of a carriage device for scanning on which the liquid ejecting device is mounted: wherein the liquid storage tank has a means to suppress unnecessary collapsed areas in the negative pressure generating member in the vicinity of the air importing portion.
The liquid storage tank, the liquid ejecting device and liquid ejecting apparatus according to the present invention constituted in the above-mentioned ways, can attain a stable ink supply, in other words, a good printing quality, since the collapse, namely, the capillary effects caused by the collapse is suppressed, thus a smooth gas/liquid exchange is attained.